Method and apparatus for controlling a motor-driven oil pump

ABSTRACT

The present invention is a method and apparatus for controlling driving of the electric oil pump. The method includes the steps of deciding whether a predetermined time has elapsed after oil supply to the hydraulic chain tensioner has stopped, deciding whether an engine start prediction signal is inputted to a controller, and driving the electric oil pump to supply oil to the hydraulic tensioner when the engine start prediction signal is inputted. The present invention insures that oil pressure is maintained in the chamber of the hydraulic tensioner before cranking of the engine, thereby preventing oscillation of the chain and tensioner piston at the time of engine start up.

REFERENCE TO RELATED APPLICATIONS

This application claims an invention which was disclosed in Japanese Application Number 2005-184241, filed Jun. 24, 2005, entitled “METHOD AND APPARATUS FOR CONTROLLING A MOTOR-DRIVEN OIL PUMP”. The benefit under 35 USC §119(e) of the Japanese application is hereby claimed, and the aforementioned application is hereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for controlling the driving of an electric oil pump in internal combustion engines.

2. Description of Related Art

Generally, in internal combustion engines, hydraulic tensioners have been used to maintain tension in timing chains that drivingly connect crankshafts to camshafts. Oil supply to the chambers of hydraulic tensioners is typically provided by a mechanical oil pump driven by the engine.

Hydraulic tensioners tend to leak oil from the chambers after a long time has elapsed once oil supply from the mechanical oil pump to the chambers ceases due after the stopping of the engine. In this case, when the engine restarts, since the mechanical oil pump cannot supply oil immediately to the chamber of the hydraulic tensioner, the chamber lacks the necessary oil pressure to prevent the piston of the hydraulic tensioner from applying sufficient tensioning force to the timing chain. As a result, during operation of the hydraulic tensioner, the piston of the hydraulic tensioner is easily pushed inwardly by the external force of the chain and the chain and piston oscillate, thereby causing noise.

In order to solve the above-mentioned problem, hydraulic tensioners with ratchet mechanisms have been developed to prevent the retraction of the piston. However, in this case, the overall structure of the hydraulic tensioner becomes complicated, resulting in higher manufacturing costs.

Recently, electric oil pumps have been employed for the purpose of lubricating various parts of the engine. For example, laid-open Japanese patent application No. 6-101606 describes the driving of an electric oil pump before an engine start up to lubricate various parts of the engine.

The present invention is directed to insuring the presence of oil in the chamber of the hydraulic tensioner before engine start up or after engine shut down by utilizing an electric oil pump.

SUMMARY OF THE INVENTION

The present invention consists of a method for controlling the driving of an electric oil pump containing the steps of first determining whether a predetermined amount of time has elapsed after the supply of oil to a hydraulic tensioner has stopped, determining whether an engine start prediction signal has been inputted to a controller once a predetermined amount of time has elapsed after oil supply to the hydraulic tensioner has stopped, and then driving the electric oil pump to supply oil to the hydraulic tensioner when the engine start prediction signal has been inputted.

In the case where oil has drained from the chamber of the hydraulic tensioner after a predetermined amount of time has elapsed from the stoppage of the supply of oil to the hydraulic tensioner, oil pressure can be restored to the chamber of the hydraulic tensioner before engine cranking by driving the electric oil pump, thus preventing oscillation of the chain and the piston of the tensioner at the time of cranking. Furthermore, since there is no need to provide a ratchet mechanism to prevent retraction of the piston of the tensioner, manufacturing cost is significantly reduced.

Prior to actually starting the engine by turning the ignition switch to the “start” position, the engine start prediction signal is inputted to a controller. Therefore, no time-lag occurs during engine start up. In contrast, in the technique disclosed by the above-mentioned Japanese patent application, the electric oil pump is driven based on a signal from the ignition switch during engine starting, and only after each part of the engine is lubricated, the starter is allowed to start the engine. As a result, when turning the ignition switch to a “start” position, the engine will not start immediately, causing a time-lag before actual engine start up.

According to the present invention, the engine start prediction signal may be either a door lock release signal, a foot brake ON signal, or an ignition key insertion signal.

According to a second aspect of the invention, a method for controlling the driving of an electric oil pump is disclosed. It comprises the steps of driving the electric oil pump to supply oil to a hydraulic tensioner prior to engine start up, and stopping the electric oil pump after a predetermined time has elapsed in the case where the engine has failed to start.

According to a third aspect of the present invention, the electric oil pump is driven for at least a predetermined amount of time after the stopping of the engine to maintain oil pressure in the hydraulic tensioner.

The apparatus of the present invention consists of an electric oil pump having an oil supply line to supply oil to a hydraulic tensioner for maintaining tension on an engine timing chain, a signal generating means for generating an engine start prediction signal, and a controller for controlling the driving of the electric oil pump so that when an engine start prediction signal from the signal generating means is inputted to the controller after a predetermined amount of time has elapsed once oil supply to the hydraulic tensioner has stopped, the electric oil pump is driven to replenish the oil supply in the hydraulic tensioner.

Even in the case where oil no longer remains in the chamber of the hydraulic tensioner due to the lapse of a predetermined amount of time after the oil supply to the hydraulic tensioner has ceased, the driving of the electric oil pump reestablishes oil pressure in the chamber of the hydraulic tensioner before engine cranking, thus preventing the oscillation of the chain and the piston of the tensioner at the time of cranking.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a block diagram of a drive-controlling system for the electric oil pump according to the present invention.

FIG. 2 is a flow diagram of a method of controlling the electric oil pump according to the present invention.

FIG. 3 is a flow diagram of a method of controlling the electric oil pump according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.

FIGS. 1 and 2 show a first embodiment of the present invention. As shown in FIG. 1, a drive-controlling system (1) has an onboard controller (2). The controller (2) is connected by an engine (E/G) start prediction signal generator (21), an ignition switch (IG SW) (22), and the other inputs (23). A voltage from a battery (24) is applied to the ignition switch (22) and the controller (2). The engine start prediction signal may be a door lock release signal, a foot brake ON signal, or an ignition key insertion signal.

Also, the controller (2) is connected to an electric oil pump (O/P with a motor) (25), a starter (27) to start the engine (E/G) (26), and the other outputs (28).

As shown in dotted lines of FIG. 1, the electric oil pump (25) has an oil supply line from an oil tank (30) connected thereto and also has an oil supply line to the hydraulic tensioner (31) connected thereto through a directional control valve (32). A mechanical oil pump (33) is drivingly connected to the engine (26). The mechanical oil pump (33) has an oil supply line from the oil tank (30) and an oil supply line to the directional control valve (32) connected thereto.

By switching the directional control valve (32) before and after engine start up, an oil supply to the hydraulic tensioner (31) is carried out by the electric oil pump (25) before engine start up and by the mechanical oil pump (33) after engine start up. A method for controlling the driving of the electric oil pump (25) will be explained hereinafter using a flow diagram shown in FIG. 2. At step S1 it is determined whether a predetermined amount of time has elapsed after oil supply to the hydraulic tensioner (31) has stopped. This predetermined amount of time is the time that is required for the oil in the chamber of the hydraulic tensioner (31) to leak out naturally.

When the predetermined time has elapsed after oil supply to the hydraulic tensioner (31) stopped, a determination is made at step S2 whether the E/G start prediction signal (e.g. a door lock release signal; a foot brake ON signal; or an ignition key insertion signal) from the E/G start prediction signal generator (21) is inputted to the controller (2).

When the E/G start prediction signal is inputted, the program moves onto step S3. At step S3, the controller (2) orders the electric oil pump (O/P) (25) on. At this time, the directional control valve (32) is switched to connect with the oil supply line from the electric oil pump (25). Thereby, oil that has been pumped up from the oil tank (30) is supplied to the chamber of the hydraulic tensioner (31) through the oil supply line and the directional control valve (32).

Then, a determination is made at step S4 whether the ignition switch (IG SW) (22) is turned to the start position to start the engine. If the engine has not been started, the program moves onto step S5 and waits for a predetermined time to elapse after the driving of the electric oil pump (25). This predetermined amount of time is set to a specific period of time at least necessary for the oil to fill in the chamber of the hydraulic tensioner. If the predetermined time has elapsed, the program moves onto step S6. At step S6, the electric oil pump (25) is stopped.

However, if the engine has been started at step S4 the program moves onto step S6. At step S6, the electric oil pump (25) is stopped. Also, if the engine is started at step S4 while the system waits a predetermined time at step S5, the program moves onto step S6 and the electric oil pump (25) is stopped. When the engine is started the directional control valve (32) is switched to the mechanical oil pump (33). Thereby, oil supply to the hydraulic tensioner (31) is carried out by the mechanical oil pump (33) and not the electric oil pump (25).

According to the foregoing embodiment, the electric oil pump (25) is driven to supply oil to the hydraulic tensioner (31) when the engine start prediction signal is inputted in the case where a predetermined time has elapsed once the oil supply to the hydraulic tensioner (31) has been stopped (see steps S1 to S3 of FIG. 2).

By so doing, even in the case where oil does not remain in the chamber of the hydraulic tensioner (31) after the predetermined time has elapsed once oil supply to the hydraulic tensioner (31) has been stopped, the driving of the electric oil pump (25) ensures the presence of oil in the chamber of the hydraulic tensioner (31) prior to cranking. In so doing, oscillation of the chain and the tensioner piston is prevented at the time of cranking. Moreover, since the electric oil pump (25) is driven for only a predetermined amount of time, in the case where the engine has failed to start, the electric oil pump (25) is not driven more than required. (see steps S3 to S6 of FIG. 2).

In another embodiment, the electric oil pump (25) may be driven along with the mechanical oil pump (33) after engine start up. In this case, by eliminating the directional control valve (32) and providing each portion of the engine with an oil supply line from the mechanical oil pump (33), whether before or after the starting of the engine, oil is supplied to the hydraulic tensioner (31) by the electric oil pump and the supply of lubricant oil to other parts of the engine is carried out by the mechanical oil pump (33).

In a further embodiment, the electric oil pump (25) may be used to supply oil not only to the hydraulic tensioner (31) but also to other parts of the engine, as well. In this case, the mechanical oil pump (33) can be eliminated.

FIG. 3 is a flow diagram of a method for controlling driving the electric oil pump after the stopping of the engine. With this method, the electric oil pump (25) is driven at step T1. Then, it is determined at step T2 whether the engine (E/G) has stopped. If the engine has stopped, a determination is made at step T3 whether a predetermined amount of time has elapsed after the engine has stopped. This predetermined amount of time is the time that is required for the timing chain to completely stop running due to inertia after engine shut down. For example, the predetermined time may be set at 1 second. If the predetermined time has elapsed after the engine has stopped, the system stops the electric oil pump (25) at step T4. In this case, when the timing chain is still running after the engine shuts down and the oil supply to the hydraulic tensioner (31) from the mechanical oil pump (33) is halted, oil pressure can be maintained in the chamber of the hydraulic tensioner (31) by the electric oil pump (25), thereby preventing oscillation of the chain and the tensioner piston when the engine comes to a full stop. 

1. A method for controlling the driving of an electric oil pump in an internal combustion engine comprising: determining whether a predetermined amount of time has elapsed after oil supply to a hydraulic tensioner has been stopped; determining whether an engine start prediction signal is inputted to a controller after a predetermined amount of time has elapsed once the oil supply to the hydraulic tensioner has been stopped; and driving the electric oil pump to supply oil to the hydraulic tensioner when the engine start prediction signal is inputted.
 2. The method of claim 1, wherein the engine start prediction signal is selected from the group consisting of a door lock release signal, a foot brake ON signal, and an ignition key insertion signal.
 3. A method for controlling the driving of an electric oil pump in an internal combustion engine comprising: driving the electric oil pump to supply oil to a hydraulic tensioner prior to an engine start up; and stopping the electric oil pump after a predetermined amount of time has elapsed when the engine has failed to start.
 4. A method for controlling an electric oil pump in an internal combustion engine comprising driving the electric oil pump for at least a predetermined amount of time after the engine has stopped.
 5. An apparatus for controlling the driving of an electric oil pump in an internal combustion engine comprising an electric oil pump having an oil supply line to supply oil to a hydraulic tensioner for maintaining tension in an engine timing chain; a signal generating means for generating an engine start prediction signal; and a controller for receiving the engine start prediction signal and for controlling the driving of the electric oil pump.
 6. The apparatus of claim 5 wherein the electric oil pump is driven for a predetermined amount of time after the input of the engine start prediction signal.
 7. The apparatus of claim 5, wherein the engine start prediction signal is selected from the group consisting of a door lock release signal, a foot brake ON signal, and an ignition key insertion signal. 